In order to improve braking performance and traction performance on a snowy road, a tire used for driving on the snowy road has conventionally been provided, in a land portion defined on a tread portion, with a plurality of sipes extending in a tire width direction so as to form edge components. One example of such a sipe is a two-dimensional sipe that has a zigzag or a wave pattern on a tread surface and that is configured by an incision extending vertically relative to the tread surface with the pattern remaining unchanged in a depth direction.
As an effective way to improve an edge effect, it is known that the number of the sipes in the land portion should be increased. However, increasing the number of the sipes in the land portion excessively will lead to subdivision of the land portion, resulting in a decrease in rigidity of the land portion. Consequently, although snow performance is improved, a footprint area of the land portion is decreased, and dry performance and wet performance might be deteriorated.
In view of the above, in recent years, there is proposed a three-dimensional sipe which has a pattern varying in the depth direction as well and in which inner walls of the subdivided land portion are brought into contact with each other so as to prevent collapse of the land portion. (Refer to Patent Literature 1, for example.)